Penal have very high rifle damage and would be punished overall by getting PPSHs imho. Will outshoot volks and grens at all ranges. If you desire a squad with close range PPSHs, there's none better than Shock Troops.
But then your penciled in to certain commanders, or people just want something different. Also with the VET1 ability of Penals wouldn't it provide more synergy then conscripts which aren't really designed for it. Why is it such a problem when their is the jaeger upgrade that can be used by all of ost.
EDIT
As an example the new Soviet Reserve army with T1 opening would allow a complete army. The penals would be the backbone with options for CQC, medium range and some AT. The team weapon drop would allow for a weak hmg and true AT along with a commisar which could boost performance of troops and provide healing. The down side would be no prem med or heavy and heavy MP load.
Advance Warfare Tactics/Conscript support tactics could have 2 different openings instead of conscript spam.